A: You're not alone in your puzzlement. Thanks to a recent Mayo Clinic study published in the Journal of Strength and Conditioning Research, we now know that the majority of people interviewed in at least one health club (and I can vouch for its clientele, since it's the one I use) were wearing weight belts at the wrong time, for the wrong reasons.
The National Strength and Conditioning Association (NSCA) recommends wearing them only for
The study found that 90 percent of current belt users thought it would help prevent injury, and 22 percent thought it helped improve performancewhen in fact the research literature is divided on both questions.
The study also found that over half of all belt users used them on lighter loads, counter to the NSCA's above advice. Moreover, some users said they would use them during exercises like the bench press when, if you're not cheating, the lower back is actually just fine on its own, thank you very much. One guy even used them during his cardio, perhaps just for his very own little treadmill/back-weakening session.
None of this should be surprising, given the way they make the employees wear them around the store at Home Depot. But it does indicate, as the authors of the study suggest, an area for better education.